Jan. 8, 2016

Bright spots seen by NASA’s Dawn spacecraft on the surface of dwarf planet Ceres are likely salt deposits. Ceres has more than 130 bright areas, and most of them are associated with impact craters. Observations from Dawn’s Framing Camera suggest the occurrence of salts originating from Ceres’ interior. These salts are consistent with a type called magnesium sulfate according to a Nature paper on which PSI’s Lucille Le Corre, Vishnu Reddy, Jian-Yang Li, David O’Brien and Mark Sykes are co-authors.
“We reviewed three possible analogs for the bright spots (ice, clays and salts),” said Le Corre, a PSI Research Scientist. “Salts seem to fit the bill and are the best possible explanation of what we see on the surface of Ceres.”

Le Corre and colleagues, using images from Dawn's framing camera, suggest that these salt-rich areas were left behind when water-ice sublimated in the past. Impacts from asteroids would have unearthed the mixture of ice and salt.
“The location of some bright spots also coincide with places where water vapor was detected by other spacecraft,” said Reddy, a PSI Research Scientist. “This gives us confidence that the bright spots are likely salt deposits left over by sublimating salty water.”